The present invention relates to improvements in systems for manually controlling the flow rate of intravenous liquid. More particularly, the present invention relates to a method and apparatus which permits a nurse or other hospital personnel to rapidly adjust a drip rate in an intravenous system to the desired rate without the need for costly and cumbersome automatic flow control devices.
It is the usual medical practice, when administering liquids intravenously, to employ an intravenous liquid injection system commonly referred to as an intravenous set. An intravenous set usually includes a bottle of the liquid to be delivered, a drip chamber, an intravenous feeding tube, and a suitable valve mechanism. The bottle is normally supported in an inverted position and includes a drop-forming member which delivers drops of the liquid into the drip chamber. The chamber in turn feeds the intravenous tube which is clamped to control the rate of intravenous liquid flow into the patient. The drip chamber serves the dual function of permitting a nurse or other attendant to observe the rate at which the liquid drops egress from the bottle, and creating a reservoir of the intravenous liquid at the lower end of the chamber to insure that no air enters the intravenous feeding tube leading to the patient. As is well understood by those skilled in the art, variations in the rate of liquid escape from the drip chamber to the feed tube control the back pressure in the drip chamber and thus govern the rate of formation of the drops egressing from the bottle. Thus, by changing the degree of clamping of the feed tube, the nurse or other attendant can control the drip rate from the bottle.
It has been the general practice in hospitals to have individuals periodically monitor the drop flow rate at each intravenous feeding station. Such monitoring of the drop flow rate is a tedious and time-consuming process which is prone to error and the possibility of serious consequences. In addition, a substantial reduction of the available time of qualified medical personnel is caused by the need to spend relatively long periods of time monitoring the drop flow rate. Typically, the nurse monitoring the drop flow rate employs a watch or clock to time the number of drops flowing from the bottle into the drip chamber during a given interval, usually one or more minutes. The nurse will then mentally perform the arithmetic computations necessary to convert the time and drop count into an appropriate parameter, for example, cubic centimeters per hour. If the calculated rate is substantially different than the prescribed rate, the nurse must manually adjust the clamp on the feed tube for a new rate, and then count the drops again and recalculate to measure the new rate. Clearly, each of the aforedescribed measurements and calculations and subsequent flow rate adjustments require several minutes time. Considering the number of stations being monitored, and the number of times per day each station must be monitored, it is apparent that a considerable portion of a nurse's time must be devoted to overseeing the delivery of intravenous liquid. In addition, under the pressure of heavy schedules, mental calculations performed by an overworked nurse may be incorrect, with the possibility of dangerous flow conditions developing.
It has been suggested in a multitude of prior art patents that the drop flow rate of intravenous liquid delivered to the patient may be automatically regulated by a suitable apparatus. Such apparatus usually employs a drop sensor which senses drops entering the drip chamber and which provides a signal from which the actual drip rate may be computed. Comparison circuitry for comparing this actual drip rate with a desired and pre-set drip rate is employed and in turn controls a mechanism such as a valve which regulates the flow through the intravenous feed tube leading to the patient. Such apparatus, in most cases, serves its intended function, namely: reducing the amount of time required by personnel to oversee the delivery of intravenous fluids to patients. However, such apparatus achieves the desired result at considerable cost. Since the apparatus cannot be time-shared for multiple concurrent use, if one hundred patients in a hospital require intravenous infusion of liquid concurrently, one hundred of these automatic control units must be available. The multiplied cost factor, for most hospitals, often outweighs the more efficient utilization of a nurse's time brought about by such units. Further, the complex electro-mechanical control arrangement is subject to failure which can have serious, and sometimes fatal, consequences.
It is an object of the present invention to provide an inexpensive approach to facilitating the manual adjustment of intravenous liquid flow rates without requiring long periods of time to make the necessary adjustments.
It is another object of the present invention to provide an apparatus which permits a nurse or other hospital attendant to easily and rapidly set the desired drip rate in an intravenous injection system.
It is another object of the present invention to provide a method for accurately, inexpensively, and quickly setting the desired drip rate in an intravenous set.